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2018 Forester 2.5i 6MT
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478 Posts
If you have a Ford truck, every 12-18 months and always carry a spare :grin2:

In all seriousness, they are a replace-as-needed item. It's very unlikely you will ever need to replace one of the ignition coils in your forester in it's lifetime. What *is* recommended is new boots if the old ones are dry cracked and putting on new dielectric grease.
 

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2018 Forester 2.5i 6MT
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478 Posts
Just a dab of dielectric grease on the part that goes on the plug and just rub some on the inside of the boot; just a small amount will keep it from corroding and also keep the boot from sticking to the plug.


I always antiseize spark plugs. And back off the torque by 1 or 2 ft/lb when I do it
 

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2010 Forester Premium X AT
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1,000 Posts
The OEM coils on my hondas seemed to fail around the 100,000 mi mark. Then with my forester, i started getting really bad idle on humid mornings starting around 110,000 mi which after much troubleshooting of connections narrowed down to a bad coil pack.

Therefore, my rule of thumb is 100,000 mi on coil packs. Sure you could probably make it further, but it's a part that will strand you, so unless its just a grocery getter, I think this is a reasonable interval. Since you really need to remove the coil pack to access and replace the PCV valve, I just do both at the same time.
 

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2010 Forester Premium X AT
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1,000 Posts
My 2015 forester manual says the following

Tightening torque:
Spark plug: 17.5 N·m (1.8 kgf-m, 12.9 ft-lb)
Ignition coil: 8.5 N·m (0.9 kgf-m, 6.3 ft-lb)


One other option for the coil is just to buy a spare and have it in the trunk at all times after 100,000mi.
 

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2015 Forester 2.5i Limited CVT
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1,797 Posts
I looked up the high tension cords for Subaru and it appears that they do not sell just the rubber boot portion.

The complete cable system must be purchased. There are other makers, like Bosch I believe. I prefer OEM. Does anyone have other information on this?
 

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2014 Forester 2.5i CVT
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453 Posts
I looked up the high tension cords for Subaru and it appears that they do not sell just the rubber boot portion.

The complete cable system must be purchased. There are other makers, like Bosch I believe. I prefer OEM. Does anyone have other information on this?
Not sure what you are referring to. All recent Subarus have a coil and boot manufactured as a single unit. One for each cylinder. There are no "high tension cords" (spark plug wires?) Just a low-voltage connector for the wiring harness to snap into.
 
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